in the leaving earth space, you can click on "Leave from" option (using the ...) and then select sirius sector block from the menu at the top. then click on the door image on the map where vulcan should be.
i hope this is right.
this should make it that you get the mission, and then, at your leisure, go to vulcan, and you can then start your mission.
basically you can create a map but the system has no way of knowing where that map is to be located.
imagine your playing a cryptic mission. you would have to go to a system be it vulcan or p'jem or bajor or whatever to enter the first map, so basically you have to tell the foundry where that map is. so you have to at least for the first part change 'whole map' into a system. click on the little box and it will take you into a list. use the drop down box to find sirius sector (or where ever you want) and then pick the system you want the mission to start from.
unless you want your character to start on earth space dock by having him talk to a contact on the station most people will not start there. as they could be anywhere in the galaxy when they choose to take your mission.
Have not created anything myself, just looking to check out what people are doing but I remember seeing a post from The Grand Nagus about having to go to a specific part of space for "a door to" the mission.